Illuminating devices for illuminating an illuminated area are known, in principle. Such illuminating devices are used, in particular, as lighting fixtures for operating rooms for illuminating an illuminated area in the form of an operating area. The goal is to provide an especially natural and bright illumination in an operating area, i.e., in the area of the surgical wound. The classical embodiment of such illuminating devices has classical illuminating means, e.g., in the form of gas discharge lamps. These gas discharge lamps are known to provide a sufficiently bright light, especially with a large blue component, and correspondingly an especially white light. The light has a good color rendering index and correspondingly high color fastness in the illuminated area. It is also known already that LEDs are used as a newer illuminating means for the illuminating devices. However, the output of an individual LED for this is not sufficient for providing the necessary brightness. Thus, a plurality of LEDs, which are arranged, e.g., in the form of a matrix, are frequently used in prior-art illuminating devices.
The drawback of prior-art illuminating devices is, on the one hand, the development of heat. A large part of the energy consumed is converted into heat especially in case of halogen lamps, but also in gas discharge lamps. The high-output LEDs needed for illuminating devices also generate a rather substantial amount of waste heat. However, the heat generated is disadvantageous, because it inconveniences the surgeon. In addition, the release of heat leads to thermal up-current, which interferes with the air flow in the area of the illuminated area. If the illuminated area is an operating area, the most sterile situation possible must be created there. If this stable situation is interfered with by thermal flows, the risk of contamination with microorganisms of the surgical wound, which is located in the illuminated area, increases. It is also disadvantageous that a rather appreciable percentage of infrared light is emitted in prior-art gas discharge lamps we well as in prior-art halogen lamps. This infrared light component leads to the risk of desiccation of the surgical wound when reaching the illuminated areas in the form of a surgical wound, and is likewise disadvantageous. Moreover, the consequence is an unpleasant scene in case of the use of LEDs and the correspondingly distributed arrangement in the corresponding light source. Thus, shadowing can be assumed here, which has an adverse effect as a partial shadowing on the color rendering and the visibility in the illuminated area for the surgeon. A complicated optical system is also necessary to bundle this plurality of LEDs and to guide them in the desired manner. This leads to markedly intensified costs in case of prior-art illuminating devices, and efficiency is reduced.